Lubricants containing deposit control additives



LUBRICANTS CONTAINING DEPOSIT CONTROL ADDITIVES Stanley R. Newman andRobert Y. Heisler, Fishkill, and Norman Alpert, Ponghkeepsie, N. Y.,assignors to The Texas Company, New York, N. Y., a corporation ofDelaware No Drawing. Application February 24, 1956 Serial No. 567,435

8 Claims. (Cl. 25256) This invention relates to a lubricating oilcontaining a novel class of additives which act to control deposits inthe combustion zone and to minimize the effects of deposits resultingfrom the combustion of the fuel particularly under low temperatureconditions. More specifically, this invention discloses that superiorlubricating oils from the standpoint of removal of low temperaturedeposits, are obtained by addition of a minor amount of polymethyleneglycol bis(glycol ether carbonate) of prescribed composition.

As auto-mobile manufacturers annually raise the compression ratio oftheir engines in the race for higher horsepower, the problem of enginedeposits resulting from the fuel becomes increasingly more severe.Engine deposits which find their origin in the fuel are primarilyresponsible for surface ignition phenomena such as preignition andoctane requirement increase (ORI) which is the tendency of sparkignition engines in service to require higher octane fuels for properperformance. There are two avenues by which this problem can beattacked. One approach is through the fuel and the other approach isthrough the lubricating oil. In our copending application filed of evendate, Serial No. 567,445, it is disclosed that superior hydrocarbonfuels from the standpoint of engine deposits result from theincorporation of polymethylene glycol bis(glycol ether carbonates) ofprescribed composition. The subject application involves the discoverythat the addition of these polymethylene glycol bis(glycol ethercarbonates) to a lubricating oil produces a lubricant marked by theability to maintain a clean engine even with dirty fuels and under lowtemperature conditions of operation.

In our copending application, Serial No. 567,476 filed of even date, nowPatent No. 2,821,539, there are disclosed novel polymethylene glycolcarbonates of the general formula wherein R is a divalent symmetricalpolymethylene radical containing at least 4 carbon atoms, R is analiphatic hydrocarbon radical containing 1 to 12 carbon atoms and n hasa value of to 10. This invention involves the discovery that aparticular group of these novel compounds, the polymethylene glycol bis(glycol ether carbonates), are deposit control lubricating oil additives.

The improved lubricating oils of this inventioircontain a polymethyleneglycol bis(glycol ether carbonate) of the general formula R'O CH CH OOCOROCO (OCH CH ),,OR

wherein R is a divalent symmetrical polymethylene radical containing atleast 4 carbon atoms and preferably 4 to carbon atoms, R is an aliphatichydrocarbon radical containing 1 to 12 carbon atoms and n has a value of1 to 6. The polymethylene glycol bis(glycol ether carbonates) areeffective in lubricating oils in concentrations as low as 0.2 volumepercent, but concentrations of 0.5 to 3.0 volume percent are normallyemployed. There is no critical upper limit of concentration, buteconomic considerations dictate that concentrations less than 5.0 volumepercent polymethylene glycol bis(glycol ether carbonate) be present inthe lubricating oil.

This invention also contemplates a process for maintaining an internalcombustion engine free from deposits, particularly those formed duringlow temperature operation, by the presence of a polymethylene glycolbis- (glycol ether carbonate) in the combustion zone. This can beeffected by using a fuel containing polymethylene glycol bis(glycolether carbonate) as disclosed in the aforedescribed co-pendingapplication, by using a lubricant containing a polymethylene glycolbis(glycol ether carbonate) as described herein, by employing a fuel andlubricant both of which contain a polymethylene glycol bis(glycol ethercarbonate) or by adding a polymethylene glycol bls( glycol ethercarbonate) to either the fuel, lubricant or both during engineoperation. In the latter mode of operation, the polymethylene glycolbis(glycol ether carbonate) is added to the gasoline in an amount toconstitute 0.01 to 1.0 volume percent of the fuel and/or to the lube toconstitute 0.5 to 5 volume percent of the lubricating oil.

The polymethylene glycol bis(glycol ether carbonates) which inhibit thedeposit-forming tendencies of hydrocarbon fuels are readily prepared bythe series of reactions described in the aforeidentified copendingapplication. In general, the preparation involves the formation of amonochloroformate by reaction of phosgene with an ethylene orpolyethylene glycol monoalkyl ether and subsequent reaction of thechloroformate with a glycol in the presence of a hydrogen chlorideacceptor such as pyridine or quinoline. An alternate reaction procedureinvolves formation of a polymethylene glycol dichloroformate by reactionof a polymethylene glycol with phosgene and subsequent reaction of thedichloroformate with a monoether of ethylene or polyethylene glycol inthe presence of a hydrogen chloride acceptor.

The lubricating oil of this invention is effective in maintainingdeposits at a low level with the result that an engine lubricatedtherewith shows exceptionally clean cylinder head, combustion space,valves and ring belt area. The low deposit level in the engine minimizessurface ignition in all its manifestations, mainly preignition andknock. In addition, the low deposit level reduces the engines octanerequirement increase. Deposits on surfaces contacted by theadditive-containing lubricating oil, such as piston skirts and cylinderwalls, are very markedly reduced.

The polymethylene glycol bis(glycol ether carbonates) usable in thelubricants of the invention are exemplified by the following:tetrarnethylene glycol bis(butoxyethyl v carbonate),

pentamethylene glycol bis(methoxyethyl carbonate), hexamethylene glycolbis(ethoxyethyl carbonate), hexamethylene glycol bis(propoxyethylcarbonate), hexamethylene glycol bis(butoxyethoxyethyl carbonate),pentamethylene glycol bis(methoxyethoxyethyl carbonate), hexamethyleneglycol bis(butoxyethoxyethyl carbonate), pentamethylene glycolbis(methoxyethoxyethyl carbonate), octamethylene glycol bis(ethoxyethylcarbonate), octamethylene glycol bis(methoxyethoxyethyl carbonate),decamethylene glycol bis(ethoxyethoxyethyl carbonate), decamethyleneglycol bis(butoxyethoxyethyl carbonate), pentamethylene glycolbis(Z-buten-loxyethyl carbonate), tetramethylene glycolbis(decoxyethoxyethyl carbonate), tetramethylene glycolbis(ethoxyethoxyethyl carbonate), pentamethylene glycolbis(butoxyethoxyethyl carbonate), pentamethylene glycolbis(octoxyethoxyethyl carbonate), pentamethylene glycol bis(pentoxyethyl carbonate), heptamethylene glycol bis (pentoxyethoxyethylcarbonate).

It is necessary for the glycol carbonate ester to have the prescribedformula in order to operate effectively as deposit-control additives. Ifthere are more than 6 ethylene oxide units, the additive becomes toowater-soluble for proper functioning as a lubricant additive.

The polymethylene glycol bis(glycol ether carbonates) etfective inreducing deposit formation in hydrocarbon fuels are all characterized byboiling points above 650 F., a molecular weight above 300 and a carbonto oxygen weight ratio below 2.5. Apparently, the glycol carbonate estermust possess all of these properties simultaneously in order to impartdeposit-forming properties to hydrocarbon fuels.

In summary, the following conclusions can be made as to the requirementsof each section of the additive molecule for the production of apolymethylene glycol bis(glycol ether carbonate) having deposit-controlproperties. (l) The polymethylene radical, that is the R group containsat least 4 and preferably less than 10 carbon atoms. The ethylene oxideunit, e. g. the -(OCH CH group, can contain 1 to 6 units. (2) Twocarbonate radicals are required since polymethylene glycol monocarbonate ester derivatives are inelfective as deposit-controladditives. (3) Terminal aliphatic radicals contain 1 to 12 carbon atomswith aliphatic radicals containing 2 to 6 carbon atoms being preferred.

The polymethylene glycol bis(glycol ether carbonates) are effective as adeposit-control additive in a concentration of at least 0.2 volumepercent of the lubricant. The concentration of the polymethylene glycolbis(glycol ether carbonate) usually falls between 0.5 and 3.0 volumepercent of the lubricant. Since the improvement in concentrations higherthan 5.0 volume percent is only marginal, a practical upper limit isabout 5.0 percent level even though there is no critical upper limit.Economic considerations also dictate that the additive concentration beless than percent.

The polymethylene glycol bis(glycol ether carbonates) of this inventionare effective in controlling deposit formation in lubricants employed inspark ignition engines, diesel motors and gas turbines. However, thepolymethylene glycol bis(glycol ether carbonates) of prescribedcomposition are normally used in motor oils for spark ignition engineswherein fuel derived deposits formed during low temperature operationare a particularly vexing problem. Diesel lubricants containingpolymethylene glycol bis(glycol ether carbonates) are effective ineliminating deposits resulting from the use of the so-' called economydiesel fuels, i. e. fuels having a high sulfur content or containingcracked or residual stocks. The polymethylene glycol bis(glycol ethercarbonates) are also useful as deposit control additives in gas turbinelubricants which are generally ester base lubricants. The polymethyleneglycol bis(glycol ether carbonates) are useful in aviation oils whichlubricate reciprocating aviation engines. The scope of the lubricatingoils to which the polymethylene glycol bis(glycol ether carbonates) ofthe invention are added to form superior lubricants is broad andincludes mineral oils, synthetic lubricating oils and mixtures thereof.

The hydrocarbon mineral oils usable in this invention can be paratfinbase, naphthene base or mixed parafiinnaphthenebase distillate orresidual oils. Paraffin base distillate lubricating oil fractions areused in the formulation of. premium grade motor oils such as arecontemplated in this invention. The lubricating base generally has beensubjected to solvent refining to improve its lubricity and viscositytemperature relationship as well as solvent dewaxing to remove waxycomponents and improve the pour of the oil. Broadly speaking, minerallubricating oils having an SUS viscosity at 100 F. be tween 50 and 1,000may be used in the formulation of the improved lubricants of thisinvention but usually the viscosity range falls between 70 and 300 at100 F.

At The mineral lubricating oils to which the polymethylene glycolbis(glycol ether carbonates) of this invention are added usually containother additives designed to impart other desirable properties thereto.For example,

' V. I. improvers such as the polymethacrylates are nor- CELL? L C O ORL wherein R is an aliphatic radical and n is an integer having a valueof more than 1.

The most commonly used detergent-dispersant additive is an alkalineearth metal sulfonate such as calcium petroleum sulfonate or bariumpetroleum sulfonate. These products are so well known asdetergent-dispersant additives they require no further description.Similarly, divalent metal alkyl phenolates are widely used as detergentseither alone or in combination with the alkaline earth metal petroleumsulfonates.

The most commonly used inhibitor and antioxidant is a divalent metalalkyl dithiophosphate which results from the neutralization of a P S-alcohol reaction product with a divalent metal or divalent metal oxide.The most widely used inhibitors are barium and zinc alkyldithiophosphates.

The synthetic lubricating oils are usually of the ester or ether type.High molecular weight, high boiling liquid aliphatic dicarboxylic acidesters possess excellent viscosity-temperature relationships andlubricating properties and are finding ever increasing utilization inlube oils adapted for high and low temperature lubrication; esters ofthis type are used in the formulation of jet engine oils. Examples ofthis class of synthetic lubricating bases are the diesters of acids suchas sebacic, adipic, azelaic, alkenyl succinic, etc.; specific examplesof these diesters are di-2-ethylhexyl sebacate, di-Z-ethylhexyl azelate,di-Z-ethylhexyl adipate, di-n-amyl sebacate, di-Z- ethylheXyl-n-dodecylsuccinate, di-2-ethoxy-ethyl sebacate, di-2'-methoxy-2-ethoxyethylsebacate (the methyl Carbitol diester), di-2'-ethyl-2-n-butoxyethylsebacate (the Z-ethylbutyl Cellosolve diester), di-2-n-butoxyethylazelate(the n-butyl Cellosolve diester) anddi-2-n-butoxy'2-ethoxyethyl-n-octyl succinate (the n-butyl Carbitoldiester).

Polyester lubricants formed by a reaction of an aliphatic dicarboxylicacid of the type previously described, a glycol and a monofunctionalaliphatic monohydroxy alcohol or an aliphatic monocarboxylic acid inspecified moi ratios are also employed as the synthetic lubricating basein the compositions of this invention; polyesters of this type aredescribed in U. S. 2,628,974. Polyesters formed by reaction of a mixturecontaining specified amounts of dipropylene glycol, sebacic acid andZ-ethylhexanol and of a mixture containing adipic acid, diethyleneglycol and 2-ethylhexanoic acid illustrate this class of syntheticpolyester lubricating bases.

Polyalkylene ethers as illustrated by polyglycols are also used as thelubricating base in the compositions of this invention. Polyethyleneglycol, polypropylene glycol, polybutylene glycols and mixedpolyethylene-polypropylene glycols are examples of this class ofsynthetic lubricat ing bases.

The sulfur analogs of the above-described diesters, polyesters andpolyalkylene ethers are also used in the formulation of the lubricatingcompositions of this invention. Dithioesters are exemplified bydi-2'ethylhexyl thiosebacate and di-n-octyl thioadipate; polyethylenethioglycol is an example of the sulfur analogs of the polyalkyleneglycols; sulfur analogs of polyesters are exemplified by the reactionproduct of adipic acid, thioglycol and 2-ethylhexyl mercaptan.

The action of the polymethylene glycol bis( glycol ether carbonate) inimproving the deposit-removing properties of a lubricating oil wasdemonstrated by a modified Chevrolet deposits testCRC EL-2-650. Thelaboratory engines are operated under the standard conditions of thistest with the exception that crankcase oil temperatures were 10 F.lower, the water jacket temperatures were 5 F. lower, and the crankcasesof the test engines were ventilated. These modifications are in everycase in the direction of making the test more severe and are intended tosimulate low temperature conditions wherein deposit formation is mostpronounced. After the termination of each run, the engine isdisassembled and its parts are evaluated by a merit system adapted fromthe CRCL-4 1252 test. This merit system involves visual examination ofthe engine part in question and their rating according to deposits bycomparison with standards which have assigned ratings. For example, arating of 10 on piston skirt designates a perfectly clean piston while arating of zero represents the worst condition. Similarly, a rating of100 on total engine deposits represents a perfectly clean engine, etc.

In the following table, there are shown the results obtained in themodified Chevrolet deposits test with lubricating oils containingvarious concentrations of polymethylene glycol bis( glycol ethercarbonates) and of polymethylene glycol bis(alkyl carbonates). Base fuelA used in this testhad an 87.0 ASTM research octane rating containing2.90 ml. of TEL per gallon, had an API gravity or 58.0 and a boilingrange between 106 and 396 F.; it was negative in the copper corrosiontest and had an oxidation stability in the ASTM test of 530 minutesminimum. Base fuel B had a 90.5 ASTM research octane rating, containing2.67 ml. of TEL per gallon, had an API gravity of 59.0 and a boilingrange between 93 and 395 F.; it was negative in the copper stripcorrosion test and had an oxidation stability of 445 minutes minimum.The base fuels also contained minor amounts of gasoline inhibitor, viz.,N,N-di-secondary butyl paraphenylene di amine, lecithin, andN,N-disalicylidene-1,2-diaminopropane.

The reference lubricating oil was a 20-20W heavy duty oil meetingsupplement I requirements. This reference oil contained a methacrylateVI improver and a balanced combination of additives which impartdetergent, dispersant and antioxidant properties to the oil. Theadditive mixtures comprises a barium petroleum sulfonate and a zincalkyl dithiophosphate in which the alkyl group is a methylcyclohexylradical.

TABLE I Engine cleanliness in the modified Chevrolet S-II testConcentra- Total tion of Addi- Piston Engine tive in Oil at SkirtDeposits Run Termination, Vol. Percent Base Oil (Fuel A) 4.7 77. 7 BaseOil (Fuel A) plus:

1, 5-pentamethylene glycol bis (Z-ethoxyethyl carbonate) 7. 8 82. 8 3 1,-pentamethy1ene glycol bis (2-ethylhexyl carbonate) 4. 7 70. 7 3 0 BaseOil (Fuel B) 6. 1 79. 9 Base Oil (Fuel B) plus:

1, S-pentamethylene glycol bis (2,2, 2-triethoxyethy1 carbonat 9. 7 90.7 2. 6 1, S-pentamethylene glycol bis (n amyl carbonates) 4. 8 76.8 3. 0

The data in the foregoing table clearly show that polynethylene glycolbis(glycol ether carbonates) are effective deposit-control additives forlubricating oils. Ratings above 7.8 in piston skirt deposits and abovein total engine deposits are very good results in this low temperaturedeposits test.

It is significant that polymethylene glycol bis(alkyl carbonates) whichare also disclosed as novel compounds in the aforeidentified copendingapplication Serial No. 567,476 are ineffective deposit-controladditives. It has been theorized that the ether linkage in thepolymethylene glycolv bis( glycol ether carbonates) is an importantfactor in the removal of deposits. Whatever the explanation of theeffectiveness of polymethylene glycol bis(glycol ether carbonates) andof the ineffectiveness of polymethylene glycol bis(alkyl carbonates),the results are striking.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritandscope thereof and, therefore, only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A lubricating oil containing a polymethylene glycol bis(glycol ethercarbonate) having a carbon to oxygen weight ratio below 2.5 and aboiling point above about 650 F. and the general formula wherein R is adivalent symmetrical polymethylene radical containing at least 4 carbonatoms and preferably 4 to 10 carbon atoms, R is an aliphatic hydrocarbonradical containing 1 to 12 carbon atoms and n has a value of 1 to 6, inan amount sufiicient to eliminate deposits formed during fuel combustionand to maintain a clean engine.

2. A lubricating oil according to claim 1 containing 0.2 to 5.0 volumepercent polymethylene glycol bis(glycol ether carbonate).

. 3. A lubricating oil according to claim 1 containing 0.5 to 30 volumepercent polymethylene glycol bis(glycol ether carbonate).

4. A mineral lubricating oil containing a polymethylene glycolbis(glycol ether carbonate) having a carbon to oxygen weight ratio below2.5 and a boiling point above about 650 F. and the general formula R'OCH CH O ,,OCOROCO (OCH CH ,,OR'

wherein R is a divalent symmetrical polymethylene radical containing atleast 4 carbon atoms and preferably 4 to 10 carbon atoms, R is analiphatic hydrocarbon radical containing 1 to 12 carbon atoms and n hasa value of l to 6, in an amount sufficient to eliminate deposits formedduring fuel combustion and to maintain a clean engine.

5. A lubricating oil according to claim 4 containing 0.2 to 5.0 volumepercent polymethylene glycol bis(glycol ether carbonate).

6. A lubricating oil according to claim 4 containing 0.5 to 3.0 volumepercent polymethylene glycol bis (glycol ether carbonate).

7. A lubricating oil according to claim 4 containing 0.2 to 5 .0 volumepercent 1,5-pentamethylene glycol bis(2- ethoxyethyl carbonate).

8. A lubricating oil according to claim 4 containing 0.2 to 5.0 volumepercent 1,5-pentamethylene glycol bis(2,2',2" triethoxyethyl carbonate).

References Cited in the file of this patent UNITED STATES PATENTS2,370,571 Muskat Feb. 27, 1945 2,379,249 Muskat June 26, 1945 2,379,250Muskat June 26, 1945 2,379,252 Muskat June 26, 1945 2,651,657 MikeskaSept. 8, 1953

1. A LUBRICATING OIL CONTAINING A POLYMETHYLENE GLYCOL BIS(GLYCOL ETHERCARBONATE) HAVING A CARBON TO OXYGEN WEIGHT RATIO BELOW 2.5 AND ABOILING POINT ABOVE ABOUT 650*F. AND THE GENERAL FORMULA